Thermoplastic film structures having improved barrier and mechanical properties

ABSTRACT

The present invention relates to thermoplastic film structures having improved barrier and/or mechanical properties and methods for making the film structures. These improvements are achieved by incorporating into the thermoplastic film structures a polymeric nanocomposite comprising a polymer and nanosize particles of a modified clay.

The present invention relates to thermoplastic film structures havingimproved barrier and/or mechanical properties and methods for making thefilm structures. These improvements are achieved by incorporating intothe thermoplastic film structures a polymeric nanocomposite comprising apolymer and nanosize particles of a modified clay.

DESCRIPTION OF THE PRIOR ART

It has been known to manufacture compositions which comprise modifiedclays in a polymeric base. These compositions are known asnanocomposites.

Carter, et al., U.S. Pat. No. 2,531,396 discloses a reinforced elastomerand a process for producing said elastomer which contains a modifiedclay. The clay of the invention includes montmorillonite, viz, sodium,potassium, lithium and other bentonites. The clay is characterized by anunbalanced crystal lattice which are believed to have negative chargesneutralized by inorganic cations.

Frisk, U.S. Pat. No. 5,916,685 discloses a transparent multilayerlaminate containing nanoparticulates having superior barrier propertiesto oxygen, water vapor and aromatic gases.

Frisk, et al., U.S. Pat. No. 5,876,812 disclose a container made ofpolymeric material which contain nanoparticulates to increase barrierproperties.

Frisk, et al., U.S. Pat. No. 5,972,448 disclose a container made from apolymer material which has been integrated with a plurality of nanosizeparticles.

Serrano, et. al., U.S. Pat. No. 5,844,032 discloses the manufacturing ofnanocomposites which are intercalated and combined with an EVOH matrixpolymer.

Beall, et al., U.S. Pat. No. 5,952,095 disclose how to make specificintercalated nanoparticulates. The disclosure teaches nanoparticulatesthemselves, as well as methods of making them in addition to organicliquid compositions containing nanoparticulates.

Beall, et al., U.S. Pat. No. 5,880,197 disclose clays treated withorganic molecules which when so treated intercalate the clay particlesto create a matrix-like structure.

Beall, et al., U.S. Pat. No. 5,877,248 disclose a method of increasingthe viscosity of an organic liquid by combining it with nanocompositematerials having specific characteristics/limitations.

Beall, et al., U.S. Pat. No. 5,578,672 disclose intercalates formed bymixing a phyllosilicate with a polymer and a liquid carrier, andextruding the mixture through a die-opening to absorb or intercalate thepolymer between adjacent phyllosilicate platelets.

Christiani, et al., U.S. Pat. No. 5,747,560 disclose a process formaking polymeric nanocomposite materials wherein the platelet particleshave an average thickness equal to or less than about 50 Å and a maximumthickness of about 100 Å.

Maxfield, et al., U.S. Pat. No. 5,514,734 disclose a process of formingnanocomposite material comprising a polymer matrix comprising apolymeric material and dispersed particles selected from the groupconsisting of platelet or fibrillar particles having specificcharacteristics.

Maxfield, et al., U.S. Pat. No. 5,385,776 disclose a composite formedfrom a gamma phase polyamide having dispersed therein a particulatematerial such as a phyllosilicate.

Alexandre, et. al., WO 99/47598, disclose a nanocomposite which is adispersion of nanofiller particles derived from layered metal oxides ormetal oxide salts. The nanocomposite is advantageously prepared by firstswelling an untreated clay in water, then removing the water to form anorganophilic clay that is dispersible in non-polar organic solvents. Theorganophilic clay can then be treated with an alkyl aluminoxane andsubsequently a catalyst to form a complex that promotes olefin orstyrenic polymerization and platelet dispersion, The nanocomposite canbe prepared directly by in situ polymerization of the olefin or thestyrene at the nanofiller particles without shear, without an ionexchange step, and without the need to incorporate polar substituentsinto the polyolefin or polystyrene.

Fischer, et al., WO 99/35185 disclose a method for preparing ananocomposite material based on a polymeric matrix and a layered doublehydroxide. The disclosure further relates to a nanocomposite materialobtainable by such method and to a shaped article manufactured from suchnanocomposite material.

Barbee, et al., WO 99/32403 disclose a composition comprising a polymerhaving dispersed therein at least one layered clay material which hasbeen cation exchanged with organic cation salts; and at least oneexpanding agent which is compatible with said polymer. Preferredpolymers include polyesters. The compositions of the disclosure showvastly improved platelet separation as evidenced by higher thanpreviously reported basal spacing. The disclosure further relates topolyester composite materials having improved barrier useful for formingpackages that have improved gas barrier properties.

Fischer, WO 99/07790 discloses a nanocomposite material on the basis ofa clay having a layered structure and a cation exchange capacity of from30 to 250 milliequivalents per 100 grams, a polymeric matrix and a blockcopolymer or a graft copolymer, which block copolymer or graft copolymercomprises one or more first structural units, which are compatible withthe clay, and one or more second structural units, which are compatiblewith the polymeric matrix. Fischer further discloses a nanocompositematerial wherein the clay has a cation exchange capacity of from 50 to200 milliequivalents per 100 gram. In addition, Fischer discloses ananocomposite material wherein the polymeric matrix is selected from thegroup consisting of polyolefins, vinyl polymers, polyesters, polyethers,polysiloxanes and acrylic polymers.

Li, et al., WO 98/53000 disclose toughened nanocomposite materials whichare prepared based on a blend of one or more thermoplastic engineeringresins, e.g., nylon, a functionalized, e.g., brominated, copolymer of aC₄-C₇ isomonoolefin, e.g., isobutylene, and a para-alkylstyrene, e.g.,para-methylstyrene, and further contain a uniformly dispersed exfoliatedphyllosilicate layered clay, e.g., montmorillonite. The nanocompositematerials exhibit superior mechanical properties, including enhancedimpact strength. The composition of this disclosure may be extruded,compression molded, blow molded or injection molded into various shapedarticles including fibers, films, industrial parts such as automotiveparts, appliance housings, consumer products, packaging and the like.The resulting articles exhibit both high impact strength and low vaporpermeability.

Matayabas, et al., WO 98/29499 disclose polyester-platelet particlecomposite compositions comprising about 0.01 to about 25 weight percentplatelet particles dispersed in at least one polyester wherein saidcomposition has an intrinsic viscosity of greater than about 0.55 dl/g,low shear melt viscosity greater than about 30,000 poise and a gaspermeability which is at least 10% lower than that of unmodifiedpolyester.

Frisk, et. al., WO 98/01346 disclose a container which is composed of apolymer material integrated with a plurality of nanosize particles of aclay mineral which act to enhance the barrier properties of thecontainer. The polymer material may be PET, COPET or any mixturethereof. The nanocomposite polymer container decreases the permeabilityof various gases without substantially altering the fabrication methodfor producing containers composed of PET or COPET material, and withoutaltering the containers themselves. The nanocomposite polymer containersof the disclosure are able to accomplish this due to the minimal amountof clay integrated with the polymer material, i.e., between 0.1% and 10%weight of the container. The small amount of clay provides a substantialbarrier due to the high aspect ratios of the clay particles which willvary between 100 and 2000. The nanocomposite polymer container may beproduced using in situ polymerization, solution intercalation, or meltexfoliation to integrate the clay mineral with the polymer materialmatrix. The clay mineral may be smectite, vermiculite, halloysite or anysynthetic analog thereof, with a preference for the montmorillonitespecies of smectite clays.

SUMMARY OF THE INVENTION

This invention relates to polymeric thermoplastic film structures havingimproved barrier and/or mechanical properties wherein at least one layerof the thermoplastic film structure comprises a polymeric nanocompositecomprising a polymer and nanosize particles of a modified clay, andmethods of making the polymeric thermoplastic film structures.

DETAILED DESCRIPTION OF THE INVENTION

Layered clay minerals such as smectite clays which are furtherexemplified by montmorillonite, nontronite, beidellite, volkonskoite,hectorite, saponite, sauconite, magadite, kenyaite and vermiculite arecomposed of packets of face to face stacking of individual silicatelayers or sheets. In nature, the metal ions are substituted for ionssuch as Mg, Fe, Mn and Li. Because of this substitution, the sheets havea negative charge imbalance that is neutralized by hydratable cationssuch as sodium and calcium. The thickness of the sheets is about 1 nmand the diameter of the sheets is typically from 50 to 1000 nm resultingin aspect ratios of 50 to 1000. These layered clay minerals are alsoknown as phyllosilicates.

It is known that these layered clay minerals can be treated with organicmolecules such as, e.g., organic ammonium ions to insert the organicmolecules between adjacent planar silicate layers thereby increasing theinterlayer spacing between the adjacent silicate layers. This process isknown as intercalation and the resulting treated clay mineral is termed“modified clay.” The thus-treated intercalated phyllosilicates haveinterlayer spacing of at least 10-20 Å and up to about 100 Å. Themodified clay may then be used in at least two distinct methods forpreparing nanocomposites, i.e., melt compounding and in situpolymerization. Both methods are known to those skilled in the art. Thepreferred method of melt compounding of nanocomposites is with atwin-screw extruder or similar blending apparatus. In order to achievegood intercalation, exfoliation and dispersion of the clay minerals,processing conditions should be such that both shear rate and residencetime are optimized.

In addition to these methods, the clay can also be incorporated intoliquid coatings or adhesives. As with melt compounding, processingconditions should be such that both shear rate and residence time areoptimized. The adhesive or coating may consist of monomer, oligomer,polymer or mixtures thereof and may undergo polymerization after it hasbeen applied to a substrate.

The amount of modified clay material combined with the polymer should bein an amount that is sufficient to provide the desired barrier and/ormechanical properties. The amount of modified clay material in thenanocomposites of the invention comprises about 0.1% to about 25% byweight of the composition. A preferred range of modified clay materialcomprises about 0.5% to about 10% of the composition.

Polymers suitable for use in the nanocomposites of the present inventionare exemplified, but not limited to, polyolefins such as low densitypolyethylene (LDPE), linear low density polyethylene (LLDPE), mediumdensity polyethylene (MDPE), high density polyethylene (HDPE), andpolypropylene (PP), polyamides such as poly(m-xyleneadipamide) (MXD6),poly(hexamethylenesebacamide), poly(hexamethyleneadipamide) andpoly(-caprolactam), polyesters such as poly(ethylene terephthalate), andpolyacrylonitriles. Other polymers suitable for use in thenanocomposites of the invention include ethylene vinyl alcoholcopolymers, ethylene vinyl acetate copolymers, polyesters grafted withmaleic anhydride, PVdC, aliphatic polyketone, and LCP (liquidcrystalline polymers). A polyketone is exemplified by Carillon® which isproduced by Shell. A liquid crystalline polymer is exemplified byVectra® which is produced by Ticona. Further polymers that may be usedinclude epoxy and polyurethane adhesives.

While certain clay minerals have been exemplified above it is understoodthat any clay mineral (both natural and synthesized) having acation-exchange capacity of 50 to 200 milliequivalent/100 g and a largecontact area with the polymer to be used in said nanocomposite areuseful in the present invention.

Definition of Terms

Unless specifically set forth and defined or otherwise limited, thefollowing terms as used herein have the following meanings.

Adhesive shall mean substances which bind/adhere; adhesives as usedherein can generally be classified either as tie resins or laminatingadhesives.

Aspect Ratio shall mean the ratio of a particular object's width to itsthickness.

Barrier shall mean a material or a material structure such as a film,layer, membrane or surface coating which prevents the penetration orpermeation of vapors or gases through or beyond the material or materialstructure acting as the barrier. Such barriers may be selective ornon-selective depending on whether or not the barrier acts to prevent aspecific (or number of specific) vapors or gases to penetrate orpermeate the barrier material or structure. Thus, a water vapor ormoisture barrier would prevent penetration or permeation by water vapor,an oxygen barrier would prevent penetration by oxygen (for example,oxygen as contained in the atmosphere), and a flavor or aroma barrierwould prevent penetration or permeation by complex organic moleculesthat impart flavor or aroma. These barriers may act to preventpenetration or permeation by vapors or gases by means of certainphysical or chemical properties that the barrier material or barrierstructure possesses.

Core or core layer shall mean an interior layer of a multilayer filmhaving an odd number of layers wherein the same number of layers ispresent on either side of the core layer.

Epoxy shall mean a compound containing an epoxide functionality.

Ethylene vinyl acetate copolymer (EVA) shall mean a copolymer formedfrom ethylene and vinyl acetate monomers wherein the ethylene derivedunits in the copolymer are present in major amounts and the vinylacetate derived units in the copolymer are present in minor amounts.

Ethylene vinyl alcohol copolymer (EVOH) shall mean a copolymer formed bythe hydrolysis of poly(vinyl acetate).

Exfoliate or exfoliated shall mean individual platelets of a modifiedclay so that adjacent platelets of the modified clay can be dispersedindividually throughout a carrier material, such as water, a polymer, analcohol or glycol, or any other organic solvent.

Exfoliation shall mean a process for forming an Exfoliate from amodified clay.

Intercalant shall mean an organic molecule such as an ammonium ion thatis absorbed between platelets of the layered material and complexes withthe Na⁺ cations on the platelet surfaces to form an Intercalate.

Intercalate or intercalated shall mean a Layered Material that includesorganic molecules disposed between adjacent platelets of the LayeredMaterial to increase the interlayer spacing between the adjacentplatelets to at least about 5 Å, preferably at least about 10 Å.

Intercalation shall mean a process for forming an Intercalate.

Interior or interior layer shall mean a layer of a multilayer film whichis not a skin or surface layer of the film.

Intermediate or intermediate layer shall mean an interior layer of amulti-layer film which is positioned between a core layer and a surfacelayer of said film.

Laminating adhesive shall mean an adhesive between two substrates;typically laminating adhesives are thermosetting polymers such aspolyurethane or epoxy that cure after they have been applied.

Layered Material shall mean an inorganic material, such as a smectiteclay mineral, that is in the form of a plurality of adjacent, boundlayers and has a thickness, for each layer, of about 3 Å to about 50 Å,preferably about 10 Å.

Matrix monomer shall mean a monomer that the Intercalate or Exfoliate ismixed with or dispersed.

Matrix polymer shall mean a thermoplastic or thermosetting polymer inwhich the Intercalate and/or Exfoliate is mixed or dispersed to form aNanocomposite.

Modified clay shall mean layered material that has undergoneintercalation.

Nanocomposite shall mean a mixture that includes a monomer, polymer,oligomer, or copolymer having dispersed therein a plurality ofindividual platelets obtained from an exfoliated modified clay.

Optical properties shall mean properties including gloss, haze andclarity (all defined by Annual ASTM Book of Standards or TAPPI TestMethods)

Platelets shall mean individual layers of the Layered Material.

Polyamides shall mean a polymer with repeating amide groups (HN-CO) suchas poly(hexamethylene sebacamide), poly(hexamethylene adipamide),poly(-caprolactam) and poly(m-xyleneadipamide), and a copolymer of Nylon6 with Nylon 6,6, which are also known as Nylon-6,10, Nylon 6,6,Nylon-6, MXD6, and Nylon 6/6,6, respectively.

Polyethylene shall mean families of resins obtained by substantiallypolymerizing the gas ethylene. By varying the comonomers, catalyst andmethods of polymerization, properties such as density, melt index,crystallinity, degree of branching, molecular weight and molecularweight distribution can be regulated over wide ranges. Polyethylenesinclude low density polyethylenes (LDPE); medium density polyethylenes(MDPE); and high density polyethylenes (HDPE). Comonomers which areuseful in the polyethylene resin family are alpha-olefins having from 4to 20 carbons.

Polyethylene terephthalate (PET) shall mean a polyester formed by thecondensation of ethylene glycol and terephthalic acid.

Polymer or polymer resin include but are not limited to, homopolymers,copolymers, such as for example, block, graft, random and alternatingcopolymers, terpolymers, etc., and blends and modifications thereof.Polymer or polymer resin shall also include all possible molecularconfigurations of the material. These structures include but are notlimited to, isotactic, syndiotactic and random molecular configurations.

Polyolefins shall mean polymers of olefins such as, for example,ethylene, propylene, butenes, isoprenes and pentenes; including but notlimited to homopolymers, copolymers, blends and modifications of saidolefins.

Polyurethane shall mean polymers containing a urethane bond.

Smectite is a 2:1 type layer silicate with an expandable latticecarrying an excess negative layer charge. The 2:1 ratio refers to alayered structure consisting of an octahedral metal oxide sheetsandwiched between two tetrahedral silicon oxide sheets.

Surface or surface layer or skin or skin layer shall mean a layer of amulti-layer film which comprises a surface thereof.

Tie resin or layer shall mean an adhesive comprised of thermoplasticpolymer that has some affinity for materials it is meant to adhere to orbind together; typically tie resins are used in coextrusion or extrusionlamination and typically are polyolefin copolymers such as EVA, EAA orEMA, or polyolefins that are grafted with maleic anhydride (examples ofgrafted materials are Plexar® from Equistar and Bynel® from DuPont).

The mechanical properties of materials for plastic packaging arephysical properties that relate to the response (deformation) of thematerial under an applied stress. Some important mechanical propertiesare tensile strength, stiffness (flexural modulus), compressivestrength, and impact resistance (toughness). Several standard ASTM testsfor measuring mechanical properties of a material are listed below.

In the packaging industry, especially, the area of flexible films havingone or more polymeric layers, there is a need to improve the barrierand/or mechanical properties of these films. It has been known to blendinorganic filler materials with a polymer material in film structures inorder to achieve these improved properties. However, this approach hasnot addressed the need completely as the inorganic filler may embrittlethe structure and/or detract from its optical properties (such as hazeand transparency). It has now been found that the incorporation ofnanosize particles of a modified clay into one or more of the polymericlayers of said film structure can improve the barrier properties withoutsacrificing, and many times improving, the mechanical, optical and otherproperties and polymeric nature of the material.

The films of the present invention have improved barrier and/ormechanical properties and comprise at least one layer comprising apolymer material integrated with a modified clay wherein the modifiedclay is between about 0.5% to about 10% by weight of the nanocompositelayer.

The clay minerals may be selected from the group consisting of smectite,vermiculite and halloysite. A preferred group is smectite clay whereinsmectite may be selected from montmorillonite, saponite, beidellitc,nontronite, hectorite and mixtures thereof. Particularly preferredsmectite clay for use in film structures is montmorillonite. The clay isusually present in a sodium ion exchange form. The clay may also betreated with an intercalant which assists in the integration of the claymineral with the polymer material. Procedures for intercalating the claymineral and forming the nanocomposites have been described earlier.

One source for the clay mineral is Southern Clay Products, Inc., ofGonzales, Tex. which markets the clay mineral under the product name“Cloisite” which are particular formulations of the clay mineral andother minor components. Another source for the clay mineral is Nanocor,Inc. of Carmel, Ind., which markets the clay under the product name“Nanomer”. However, those skilled in the art will recognize that manysources of the clay mineral are available and those sources may havetheir own particular formulations which are not outside the scope of thepresent invention.

The film structures may consist of one or more polymeric layers whereinone or more of these layers may comprise a polymeric material integratedwith nanosize particles of a modified clay mineral between about 0.5% toabout 10% weight of the layer. The nanosize particles of clay have athickness of between about 3 Å and about 50 Å, and an aspect ratio ofbetween about 50 and about 1,000.

Polymers suitable for use in the nanocomposites of the present inventionare exemplified, but not limited to, polyolefins such as low densitypolyethylene (LDPE), linear low density polyethylene (LLDPE), mediumdensity polyethylene (MDPE), high density polyethylene (HDPE), andpolypropylene (PP), polyamides such as poly(m-xyleneadipamide) (MXD6),poly(hexamethylenesebacamide), poly(hexamethyleneadipamide) andpoly(-caprolactam), polyesters such as poly(ethylene terephthalate), andpolyacrylonitriles. Other polymers suitable for use in thenanocomposites of the invention include ethylene vinyl alcoholcopolymers, ethylene vinyl acetate copolymers, polyesters grafted withmaleic anhydride, PVdC, aliphatic polyketone, and LCP (liquidcrystalline polymers). A polyketone is exemplified by Carillon® which isproduced by Shell. A liquid crystalline polymer is exemplified byVectra® which is produced by Ticona. Further polymers that may be usedinclude epoxy and polyurethane adhesives.

While certain clay minerals have been exemplified above it is understoodthat any clay mineral (both natural and synthesized) having acation-exchange capacity of 50 to 200 milliequivalent/100 g and a largecontact area with the polymer to be used in said nanocomposite areuseful in the present invention.

Film structures of the present invention may be produced by methodswhich are known in the art. These methods can be exemplified, but notlimited to coextrusion, extrusion, extrusion coating, extrusionlamination, adhesive lamination and the like, and any combination of theabove-described methods. Nanocomposite materials may also be producedvia extrusion coating and lamination techniques. Various applicationmethods such as roll coating, slot die coating, rotogravure coating, andflexographic coating may be used to produce nanocomposite adhesives andcoatings. The film structures of the present invention may also beoriented and/or cross-linked. The orientation of the film may beaccomplished at any state of the process (i.e., the total film structuremay be oriented or an individual layer or layers may be oriented priorto their inclusion in the total film structure).

The film structures of the present invention wherein one or more layerscomprise a polymer material integrated with a modified clay have manyapplications in the packaging industry. These applications can beexemplified but not limited to drug packaging, inner liners for crackersand cereal, packaging for meats and cheese, boil-in bags, heatshrinkable films, heat shrinkable bags, dry foods, pouches, andthermoformed packages.

The nanocomposite layer or layers of the film structures of the presentinvention may comprise any layer or layers of the film structure such asthe core layers, barrier layer, the sealant layer and the abuse layer.Also, the nanocomposite layer or layers may also comprise an adhesivelayer or layers of the film structure. The nanocomposite layer may alsocomprise a coating which is applied to a film structure.

In order to evaluate the barrier and/or mechanical properties of thefilm structures of the present invention the following tests can beemployed.

ASTM F1249 is a test for determining the rate of water vaportransmission through flexible barrier materials. The water vaportransmission rate is defined as the time rate of water vapor flow normalto the surfaces, under steady-state conditions, per unit area.

ASTM D3985 is a test method which covers a procedure for determinationof the steady-state rate of transmission of oxygen gas through plasticfilms. The oxygen transmission rate is defined as the quantity of oxygengas passing through a unit area of the parallel surfaces of a plasticfilm per unit time under the conditions of the D3985 test method.

ASTM D638 is a test method which covers the determination of the tensileproperties of unreinforced and reinforced plastics in the form ofdumb-bell shaped test specimens when tested under defined conditions ofpretreatment, temperature, humidity, and testing machine speed. Ingeneral, this test measures the uniaxial strain (elongation) of thesample as a function of applied stress.

ASTM D790 is a test method which covers the determination of theflexural properties of unreinforced and reinforced plastics, fromsamples generally in the form of rectangular bars molded directly or cutfrom sheet or plate stock. In general, this test measures the stiffness,or the resistance of a material to bending.

ASTM D648 is a test method which covers the determination of thetemperature at which an arbitrary deformation occurs when specimens aresubjected to a particular set of testing conditions. This test providesa measure of the temperature stability of a material, i.e., thetemperature below which the material does not readily deform under astandard load conditions.

Preferred embodiments of film structures having improved barrier ormechanical properties of the present invention are presented in thefollowing examples, which are presented for illustrative purposes onlyand are not intended to limit the invention in any manner.

EXAMPLE 1

By coextrusion, a five layer thermoplastic nanocomposite film structurehaving improved gas barrier properties was produced comprising a firstlayer of EVA and an antiblock agent (EVA LD-302.56 from Exxon; antiblock10710 from Ampacet); a second layer of EVA grafted maleic anhydride(Plexar 108 from Equistar); a third layer of 95 wt. % MXD6 (MXD6-6007from Mitsubishi) and 5 wt. % of a modified clay (Cloisite from SouthernClay Products, Inc.); a fourth layer of EVA grafted maleic anhydride(Plexar 108 from Equistar); and a fifth layer of EVA (LD-302.56 fromExxon). The modified clay mineral (montmorillonite) was mixed with theMXD6 by a twin screw extrusion process. Another modified clay mineralthat was used in this Example was obtained from Nanocor, Inc., under theproduct name Nanomer. The film structure of Example 1 has the followingspecification.

Film Layer Resin Layer Resin Layer Layer Density % of % of Density Wt %Wt % Weight Weight Caliper Resin (g/cc) Layer Web (g/cc) of Web of Web(lbs/rm) (lbs/rm) (mil) Layer 1 LD-302.56 0.926 96.00 30.0 0.9270 27.9529.12 7.92 8.25 0.57 inside 10710 0.926 4.00 1.16 0.33 Total 100.00Layer 2 Plexar 108 0.932 100.00 10.0 0.9320 9.76 9.76 2.76 2.76 0.19Total 100.00 Layer 3 MXD6 nanocomposite 1.198 100.00 10.0 1.1979 12.5412.54 3.55 3.55 0.19 Total 100.00 Layer 4 Plexar 108 0.932 100.00 10.00.9320 9.76 9.76 2.76 2.76 0.19 Total 100.00 Layer 5 LD-302.56 0.927100.00 40.0 0.9270 38.82 38.82 11.00 11.00 0.76 outside Total BasisWeight 37.26 Total Caliper 1.90

EXAMPLE 2

By coextrusion, a five layer thermoplastic nanocomposite film structurehaving improved gas barrier properties was produced comprising a firstlayer of EVA and an antiblock agent (EVA LD-302.56 from Exxon; antiblock10710 from Ampacet); a second layer of EVA grafted maleic anhydride(Plexar 108 from Equistar); a third layer of 80 wt. % of a nanocompositemade of 95 wt. % MXD6 (MXD6-6007 from Mitsubishi) and 5 wt. % of amodified clay (Cloisite from Southern Clay Products, Inc.) and 20 wt. %of Nylon 6 (B135TP from Honeywell); a fourth layer of EVA grafted maleicanhydride (Plexar 108 from Equistar); and a fifth layer of EVA(LD-302.56 from Exxon). The modified clay mineral (montmorillonite) wasmixed with the MXD6 by a twin screw extrusion process. Another modifiedclay mineral that was used in this Example was obtained from Nanocor,Inc., under the product name Nanomer. The film structure of Example 2has the following specification.

Film Layer Resin Layer Resin Layer Layer Density % of % of Density Wt %Wt % Weight Weight Caliper Resin (g/cc) Layer Web (g/cc) of Web of Web(lbs/rm) (lbs/rm) (mil) Layer 1 LD-302.56 0.927 96.00 30.0 0.9270 28.0129.18 7.92 8.25 0.57 inside 10710 0.926 4.00 1.17 0.33 Total 100.00Layer 2 Plexar 108 0.932 100.00 10.0 0.9320 9.78 9.78 2.76 2.76 0.19Total 100.00 Layer 3 MXD6 nanocomposite 1.198 80.00 10.0 1.1777 9.8911.84 2.84 3.49 0.19 B135TP 1.097 20.00 1.96 0.65 Total 100.00 Layer 4Plexar 108 0.932 100.00 10.0 0.9320 9.78 9.78 2.76 2.76 0.19 Total100.00 Layer 5 LD-302.56 0.927 100.00 40.0 0.9270 38.91 38.91 11.0011.00 0.76 outside Total Basis Weight 28.26 Total Caliper 1.90

EXAMPLE 3

By coextrusion, a five layer thermoplastic nanocomposite film structurehaving improved gas barrier properties was produced comprising a firstlayer of EVA and an antiblock agent (EVA LD-302.56 from Exxon; antiblock10710 from Ampacet); a second layer of EVA grafted maleic anhydride(Plexar 108 from Equistar); a third layer of 50 wt. % of a nanocompositemade of 95 wt. % MXD6 (D6-6007 from Mitsubishi) and 5 wt. % of amodified clay (Cloisite from Southern Clay Products, Inc.) and 50 wt. %of Nylon 6 (B135TP from Honeywell); a fourth layer of EVA grafted maleicanhydride (Plexar 108 from Equistar): and a fifth layer of EVA(LD-302.56 from Exxon). The modified clay mineral (montmorillonite) wasmixed with the MXD6 by a twin screw extrusion process. Another modifiedclay mineral that was used in this Example was obtained from Nanocor,Inc., under the product name Nanomer. The film structure of Example 3has the following specification.

Film Layer Resin Layer Resin Layer Layer Density % of % of Density Wt %Wt % Weight Weight Caliper Resin (g/cc) Layer Web (g/cc) of Web of Web(lbs/rm) (lbs/rm) (mil) Layer 1 LD-302.56 0.927 96.00 30.0 0.9270 28.1029.27 7.92 8.25 0.57 inside 10710 0.926 4.00 1.17 0.33 Total 100.00Layer 2 Plexar 108 0.932 100.00 10.0 0.9320 9.81 9.81 2.76 2.76 0.19Total 100.00 Layer 3 MXD6 nanocomposite 1.198 50.00 10.0 1.1475 6.0410.94 1.78 3.40 0.19 D135TP 1.097 50.00 4.91 1.63 Total 100.00 Layer 4Plexar 108 0.932 100.00 10.0 0.9320 9.81 9.81 2.76 2.76 0.19 Total100.00 Layer 5 LD-302.56 0.927 100.00 40.0 0.9270 39.03 39.03 11.0011.00 0.76 outside Total Basis Weight 28.17 Total Caliper 1.90

EXAMPLE 4

By extrusion, a monolayer thermoplastic nanocomposite film structurehaving improved moisture barrier is produced comprising(poly)acrylonitrile and a modified clay mineral. The clay mineral ismontmorillonite obtained from Southern Clay Products, Inc., under theproduct name Cloisite or from Nanocor, Inc., under the product nameNanomer. The modified clay mineral is 5% by weight of the filmcomposition. In this Example and in Examples 5-18, the modified clay ismixed with the matrix polymer by twin screw extrusion compounding.

EXAMPLE 5

By coextrusion, a three layer thermoplastic nanocomposite film structurehaving improved heat resistance and cuttability is produced comprisingthe first sealant layer of Example 1; a second layer of polypropylene,regrind of the entire film, and a modified clay; and a third layer ofpolypropylene and a modified clay. The modified clay is 2% by weight ofeach of the nanocomposite layers. The modified clay mineral ismontmorillonite obtained from Southern Clay Products, Inc., under theproduct name Cloisite or from Nanocor, Inc., under the product nameNanomer.

EXAMPLE 6

By coextrusion, a five layer thermoplastic nanocomposite film structurehaving improved gas and flavor barrier is produced comprising a firstlayer of HDPE; a second tie layer of Plexar 108; a third layer of MXD6and a modified clay (montmorillonite from Southern Clay Products, Inc.,under the product name Cloisite or from Nanocor, Inc., under the productname Nanomer); a fourth tie layer of Plexar 108; and a fifth sealantlayer of EVA. The modified clay is 5% by weight of the nanocompositelayer.

EXAMPLE 7

Following the procedure of Example 6, a thermoplastic film structure isproduced wherein the modified clay is present in the HDPE layer of saidfilm structure. The modified clay is 5% by weight of the nanocompositelayer.

EXAMPLE 8

Following the procedure of Example 6, a thermoplastic film structure isproduced wherein the modified clay is present in both the HDPE layer andthe MXD6 layer. The modified clay is 5% by weight of each nanocompositelayer.

EXAMPLE 9

By coextrusion, a five layer thermoplastic nanocomposite film structurehaving improved moisture and flavor barrier is produced comprising afirst layer of HDPE; a second tie layer of Plexar 108; a third layer ofEVOH and a modified clay (montmorillonite obtained from Southern ClayProducts, Inc., under the product name Cloisite or from Nanocor, Inc.,under the product name Nanomer); a fourth tie layer of Plexar 108; and afifth sealant layer of EVA. Alternatively, the modified clay is providedin the HDPE layer of the five layer film, either in addition to or tothe exclusion of the modified clay in the EVOH layer. The modified clayis 5% by weight of each nanocomposite layer.

EXAMPLE 10

By coextrusion, a three layer thermoplastic nanocomposite film structurehaving improved moisture and flavor barrier is produced comprising afirst layer of HDPE and a modified clay (montmorillonite obtained fromSouthern Clay Products, Inc., under the product name Cloisite or fromNanocor, Inc., under the product name Nanomer); a second layer of HDPEplus trim; and a third sealant layer of EVA. The modified clay is 5% byweight of the nanocomposite layer.

EXAMPLE 11

By coextrusion, a three layer thermoplastic nanocomposite film structurehaving improved heat resistance and gas barrier is produced comprising afirst layer of MXD6 and a modified clay (montmorillonite obtained fromSouthern Clay Products, Inc., under the product name Cloisite or fromNanocor, Inc., under the product name Nanomer); a second tie layer ofPlexar 108; and a third sealant layer of EVA. The modified clay is 10%by weight of the nanocomposite layer.

EXAMPLE 12

By coextrusion, a four layer thermoplastic nanocomposite film structurehaving improved heat resistance and gas barrier is produced comprising afirst layer of MXD6; a second layer of EVOH and a modified clay(montmorillonite obtained from Southern Clay Products, Inc., under theproduct name Cloisite or from Nanocor, Inc., under the product nameNanomer); a third tie layer of Plexar 108; and a fourth sealant layer ofEVA. Alternatively, the modified clay is provided in the MXD6 layer ofthe four layer film, either in addition to or to the exclusion of themodified clay in the EVOH layer. The modified clay is 5% by weight ofeach nanocomposite layer.

EXAMPLE 13

By coextrusion, a five layer thermoplastic nanocomposite film structurehaving improved heat resistance and gas barrier is produced comprising afirst layer of MXD6; a second tie layer of Plexar 108; a third layer ofEVOH and a modified clay (montmorillonite obtained from Southern ClayProducts, Inc., under the product name Cloisite or from Nanocor, Inc.,under the product name Nanomer); a fourth tie layer of Plexar 108; and afifth sealant layer of EVA. Alternatively, the modified clay is providedin the MXD6 layer of the five layer film, either in addition to or tothe exclusion of the modified clay in the EVOH layer. The modified claymineral is 10% by weight of each nanocomposite layer.

EXAMPLE 14

By coextrusion, a seven layer thermoplastic nanocomposite film structurehaving improved heat resistance and gas barrier is produced comprising afirst layer of MXD6; a second tie layer of Plexar 108; a third interiorlayer of MXD6 and a modified clay (montmorillonite obtained fromSouthern Clay Products, Inc., under the product name Cloisite or fromNanocor, Inc., under the product name Nanomer); a fourth core layer ofMXD6; a fifth interior layer of MXD6; a sixth tie layer of Plexar 108and a seventh sealant layer of EVA. Alternatively, the modified clay isprovided in any or all of the MXD6 layers of the seven layer filmstructure. The modified clay is 5% by weight of each nanocompositelayer.

EXAMPLE 15

A seven layer thermoplastic nanocomposite film structure is producedaccording to Example 14, except that the fourth core layer issubstituted with EVOH and a modified clay. Alternatively, the core layerof EVOH and a modified clay is either in addition to or to the exclusionof the modified clay in any or all of the MXD6 layers of the seven layerfilm structure. The modified clay is 5% by weight of each nanocompositelayer.

EXAMPLE 16

By coextrusion, a five layer thermoplastic nanocomposite film structurehaving improved gas barrier is produced comprising a first layer ofLDPE; a second tie layer of Plexar 108; a third layer of EVOH and amodified clay (montmorillonite obtained from Southern Clay Products,Inc., under the product name Cloisite or from Nanocor, Inc., under theproduct name Nanomer); a fourth tie layer of Plexar 108; and a fifthsealant layer of EVA. The modified clay is 5% by weight of thenanocomposite layer.

EXAMPLE 17

A six layer thermoplastic nanocomposite film structure having improvedheat resistance and gas barrier is produced according to Example 15, byeliminating the nylon layer between the EVOH and the tie/sealant layers.As in Example 15, the six layer film has at least one layer of nylon anda modified clay and/or one layer of EVOH and a modified clay. Themodified clay is 5% by weight of each nanocomposite layer.

EXAMPLE 18

By extrusion, a monolayer thermoplastic nanocomposite film structurehaving improved stiffness, heat resistance and moisture barrier isproduced comprising a layer of polypropylene and a modified clay(montmorillonite obtained from Southern Clay Products, Inc., under theproduct name Cloisite or from Nanocor, Inc., under the product nameNanomer). The modified clay is 5% by weight of the nanocomposite layer.

EXAMPLE 19

By lamination, a four layer thermoplastic laminate nanocomposite filmstructure is produced comprising a first film of biaxially oriented PET;a second layer of ink; a third adhesive layer of polyurethane and amodified clay (montmorillonite obtained from Southern Clay Products,Inc., under the product name Cloisite or from Nanocor, Inc., under theproduct name Nanomer); and a fourth sealant film of LDPE. Alternatively,the fourth sealant film is a single or multilayer film of LLDPE, LDPE,EVA or blend thereof. The modified clay is 2.5% by weight of thenanocomposite layer.

EXAMPLE 20

By lamination, a four layer thermoplastic laminate nanocomposite filmstructure is produced comprising a first film of oriented polypropylene(OPP); a second layer of ink; a third adhesive layer of polyurethane anda modified clay (montmorillonite obtained from Southern Clay Products,Inc., under the product name Cloisite or from Nanocor, Inc., under theproduct name Nanomer); and a fourth sealant film of LDPE. Alternatively,the fourth sealant film is a single or multilayer film of LLDPE, LDPE,EVA or blend thereof. The modified clay is 0.5% by weight of thenanocomposite layer.

EXAMPLE 21

By lamination, a four layer thermoplastic laminate nanocomposite filmstructure is produced comprising a first film of biaxially orientedNylon 6; a second layer of ink; a third adhesive layer of epoxy and amodified clay (montmorillonite obtained from Southern Clay Products,Inc., under the product name Cloisite or from Nanocor, Inc., under theproduct name Nanomer); and a fourth sealant film of LDPE. Alternatively,the fourth sealant film is a single or multilayer film of LLDPE, LDPE,EVA or blend thereof. The modified clay is 5% by weight of thenanocomposite layer.

EXAMPLE 22

Nanocomposites of the present invention may also be present in coatingswhich are applied to a film structure. Examples of coating materials andmethods of application are given below.

Coating—UV Cure

Coating—UV cure epoxy:—V113-114G UV Barrier Varnish from PPG Industries,Inc.

Substrate:—corona treated PET film.

Method:—Nanomer from Nanocor is incorporated into UV cure epoxy at 2.5%by weight. Mixed via high shear blender. Coating applied to PET bywire-wound rod and subsequently cured using a UV source.

Result:—15% improvement in oxygen barrier with no loss of transparencywhen applied to the PET film.

Coating—Vinyl Lacquer

Coating—vinyl lacquer:—mixture of acid-modified vinyl chloride-vinylacetate copolymer resin with a vinyl solution and a plasticizer.

Substrate:—foil.

Method:—Cloisite from Southern Clay Products is incorporated into vinyllacquer and a solution of methyl ethyl ketone (MEK) at 2% by weightloading relative to the dry lacquer. Mixed via high shear blender.Coating applied with wire-wound rod and subsequently dried.

We claim:
 1. A thermoplastic film comprising a barrier layer, selectedfrom the group consisting of oxygen, gas, flavor, and aroma barriers,the barrier layer comprising a polymeric nanocomposite wherein saidpolymeric nanocomposite comprises a polymer wherein said polymer isselected from the group consisting of polyacrylonitrile copolymer,polyamides, ethylene vinyl alcohol copolymers, ethylene vinyl acetatecopolymers, polyesters grafted with maleic anhydride, PVdC, aliphaticpolyketones and liquid crystalline polymers, and nanosize particles of amodified clay.
 2. The thermoplastic film of claim 1 wherein the barrierlayer comprises a surface layer of said thermoplastic film.
 3. Thethermoplastic film of claim 1 wherein the barrier layer comprises aninterior layer of said film.
 4. The thermoplastic film of claim 1wherein the polymer comprises a polyacrylonitrile copolymer.
 5. Thethermoplastic film of claim 1 wherein the polymer comprises a polyamide.6. The thermoplastic film of claim 5 wherein the polyamide is selectedfrom the group consisting of Nylon-6,10, Nylon 6,6, Nylon-6, MXD6, andNylon 6/6,6.
 7. The thermoplastic film of claim 1 wherein the polymercomprises ethylene vinyl alcohol copolymer.
 8. The thermoplastic film ofclaim 1 wherein the clay mineral comprises a phyllosilicate.
 9. Thethermoplastic film of claim 8 wherein the phyllosilicate comprisesmontmorillonite.
 10. A thermoplastic film comprising a moisture barrierlayer, the moisture barrier layer comprising a polymeric nanocompositewherein said polymeric nanocomposite comprises a polymer wherein saidpolymer is selected from the group consisting of polyacrylonitrilecopolymer, polyamides, ethylene vinyl alcohol copolymers, ethylene vinylacetate copolymers, polyesters grafted with maleic anhydride, PVdC,aliphatic polyketones and liquid crystalline polymers, and nanosizeparticles of a modified clay.
 11. A thermoplastic laminate filmcomprising at least one adhesive layer, the adhesive layer comprising apolymeric nanocomposite comprising a polymer and nanosize particles of amodified clay.
 12. The thermoplastic laminate film of claim 11 whereinthe polymer is selected from the group consisting of polyurethane andepoxy based adhesives.
 13. A thermoplastic film comprising a coatinglayer on the surface layer of said film, the coating layer comprising apolymeric nanocomposite comprising a polymer wherein said polymer isselected from the group consisting of polyacrylonitrile copolymer,polyamides, ethylene vinyl alcohol copolymers, ethylene vinyl acetatecopolymers, polyesters grafted with maleic anhydride, PVdC, aliphaticpolyketones and liquid crystalline polymers, and nanosize particles of amodified clay.